Succinic acid, also referred to as amber acid, is a dicarboxylic acid. It is an important C4 platform compound, which can be used for surfactant, detergent additive, and foaming agent etc. As ion chelating agent, it can be used for the electroplating industry. In the food service industry, it can be used as acidifier, pH modifier, flavor substance, and foodstuff modifier. It can also be used for production of medicine, antibiotics, amino acid, and vitamin.
There are two main methods for succinic acid production: chemical synthesis and micro-organism fermentation. The chemical method normally adopts butane and maleic anhydride for production by electrolysis. This method causes serious pollution, and has low conversion rate and high costs, seriously limiting the development of succinic acid market. Regarding production of succinic acid by micro-organism fermentation, since supply of raw materials is wide and cheap, this process is environment-friendly and has light pollution, and fixed CO2 can be absorbed during fermentation, thus effectively mitigating greenhouse effect, this method is a new way of utilization of the greenhouse gas of CO2 and has become a hot point of research in recent years. Since Escherichia coli has clear heredity background; is easy to operate, adjust, control, and cultivate; has simple requirements; and grows fast, it has been widely used in research in recent years, to obtain excellent strain that produces succinic acid.
The fermentation liquid that produces succinic acid by micro-organism fermentation needs to undergo pre-filtering, ultrafiltration, nano-filtration, concentration, and crystallization, to finally yield disodium succinate or succinic acid. During concentration of fermentation liquid, large amount of evaporated water and steam condensate is obtained. This evaporated water contains small amount of organic acids such as acetic acid and formic acid. Use of this water for aerobic cultivation of cells can promote cell metabolic capability by improving activity of some key enzymes in the cell, so that acid production performance of thalli is improved. Steam condensate generated during separation of succinic acid fermentation liquid does not contain organic acid or metallic ion, so that when used for thalli fermentation, osmotic pressure of the fermentation system will not increase. This condensate can be used for anaerobic fermentation stage of cells.